The role of neo-sex chromosome architecture in promoting mitonuclear co-adaptation in Eopsaltria australis. Eopsaltria australis

The genome assembly of a female Eastern Yellow Robin Eopsaltria australis from the coastal lineage complements one from the inland lineage that is already publicly available. This species has recently emerged as a highly promising model for testing hypotheses around the importance of mitonuclear interactions in speciation, because its distribution exhibits a pattern of mitochondrial differentiation that is closely associated with different thermal conditions in coastal and inland environments, rather than a north-south geographic cline as most of its nuclear background does. One nuclear region on the Eastern Yellow Robin chromosome, homologous with passerine chromosome 1A, follows the pattern of spatial differentiation seen in the mitogenome and is located on a neo-sex chromosome system at least in the inland lineage, in which the majority of chromosome 1A has fused with the ancestral passerine sex chromosomes. Sex linkage has been postulated to play an outsized role in reproductive isolation and speciation processes, and we formulated specific hypotheses in this study to test whether neo-sex chromosome architecture is associated with increased rates of divergence between lineages, particularly on nuclear-encoded genes with mitochondrial function.

东黄鸲（Eopsaltria australis）沿海种群雌性个体的基因组组装序列，可与已公开的内陆种群基因组组装序列形成互补。该物种现已成为检验物种形成过程中核质互作（mitonuclear interactions）重要性相关假说的极具潜力的研究模型：其分布呈现出与沿海、内陆环境温度差异紧密相关的线粒体分化模式，而非多数核基因组背景所呈现的南北地理渐变格局。东黄鸲的某一核区域与雀形目1A号染色体同源，该区域呈现出线粒体基因组（mitogenome）所见的空间分化模式，且至少在内陆种群中位于新性染色体（neo-sex chromosome）系统上——在内陆种群中，绝大多数1A号染色体片段已与祖先雀形目的性染色体发生融合。已有假说提出性连锁（sex linkage）在生殖隔离（reproductive isolation）与物种形成过程中发挥着远超预期的关键作用，本研究据此提出具体假说，旨在检验新性染色体结构是否与种群间分化速率提升存在关联，尤其针对携带线粒体功能的核编码基因。